Reducing semiconductor optical amplifier-induced crosstalk in wavelength division multiplexing links

Modern medium-to-long haul high capacity optical communication links based on Wavelength Division Multiplexing (WDM) technology rely on all-optical amplification of signals along the line.{09}Attractive features of Semiconductor Optical Amplifiers (SOAs) such as compact size, broad and tunable gain spectrum, and high efficiency make them natural candidates for optical amplifiers in WDM systems. However, the SOA performance suffers from strong interchannel crosstalk caused by Cross-Gain Modulation (XGM). We performed an in-depth study on SOA-induced crosstalk in WDM links and came up with two solutions.; The first one amounts to a novel fiber dispersion management scheme. It achieves crosstalk reduction by configuring the residual fiber dispersion to break up the bit pattern repetition and thus suppress the XGM. It may be potentially employed in long-haul WDM links where SOAs work as in-line amplifiers. For SOAs used as preamplifiers and in-line amplifiers in local/metropolitan transmission links, we proposed another crosstalk mitigation technique utilizing the type-II Quantum-Well (QW) structure, which is characterized by a decreased overlap between electron and hole wavefunctions. The type-II QW SOA exhibits a longer carrier lifetime and a lower differential gain, which can effectively reduce the XGM-induced crosstalk. A SOA based on a three-constituent AlGaInAs/AlGaAsSb/AlInAs type-II quantum-well active region has been designed.; In order to ascertain the efficiencies of the proposed crosstalk mitigation techniques, a new modeling method called the rectangular window averaging has been developed. Simulations using this method show that both techniques significantly lower the SOA-induced crosstalk and improve the bit error rate performance of WDM links.